The 6.8SPC is a 270 caliber round. Its basically fly's with the same as a 77 SMK in .223rem with twice the hitting force.

So you are looking at 20.5 MOA to 600yds. I think the 600yd mark is the cut off for it.

A company down the road from me http://www.ko-tonics.com/index.html only deals in 6.8SPC. I like the round and the uppers are just as well built and any I have seen. This is a great source of information on the 6.8SPC. Article in .pdf the 6.8SPC has the same recoil as a .223 so not loss there like in most AR-10 weapon systems.

I see the 6.8SPC filling three roles.

1. home protection:
the round is much harder hitting and can be handloaded or can be found in factory loadings with some great hunting bullets. This would be a better choice over the 45grn or 55grn .223rem rounds for in a building shooting.

2. Hunting:
You can now take out your favorite AR-15 and hunt deer. the .270 cal bullets are very well known to take down deer and other wildlife.

3. Competition shooting.
As we all know a bigger hole lets you have a better score if the bullet is on the scoring ring. Most three gun matches round up. So if a .224 hole and a .277 hole both hit the same place the .277 can bleed over to the scoring line.
same argument over using a .45 ACP than a 9mm in IDPA.

The 6.8 is no barn burner, but coupled with the ar's quick handling, light recoil, and light weight it's tops in my book.
At least for medium game. Bout the same energy as the 30-30 at the muzzle and a little more at range. 300yds its bout equal to the 44 mag.at the muzzle. and bout twenty five percent more energy than 5.56. Used it for deer hunting this year and I love it. puts em down. Legal to use also, so will be using it exclusively next year for everything cept elk. hth.